Educational Product 

Educators Grades 5–8 

Precipitation 

Investigating the Climate System 

Precipitation

“The Irrational Inquirer” 

PROBLEM-BASED 

CLASSROOM MODULES 

Responding to National Education Standards in: 

English Language Arts ◆ Geography ◆ Mathematics 

Science ◆ Social Studies 
Investigating the Climate System


Precipitation Precipitation

“The Irrational Inquirer” 

Authored by: 

Mary Cerullo, Resources in Science 

Education, South Portland, Maine 

Prepared by: 

Stacey Rudolph, Senior Science
 Prerequisite Knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Education Specialist, Institute for


. . . . . . . . . . . . . . . . . 5

(IGES), Arlington, Virginia


Global Environmental Strategies
 Additional Prerequisite Knowledge and Facts 

John Theon, Former Program


Scientist for NASA TRMM
 Part 1: How are rainfall rates measured? . . . . . . . . . . . . . . . . . . . . . . 6

Editorial Assistance, Dan Stillman,


Science Communications Specialist,


Institute for Global Environmental


Strategies (IGES), Arlington, Virginia


Graphic Design by: 

Susie Duckworth Graphic Design &
 of rainfall determined? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Illustration, Falls Church, Virginia


Funded by:
 Activity One; Activity Two. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

NASA TRMM Grant #NAG5-9641 

Give us your feedback: 

To provide feedback on the modules
 Activity One; Activity Two . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

educational_product
 Unit Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

and click on “Investigating the


Climate System.”
 Appendix A: Bibliography/Resources . . . . . . . . . . . . . . . . . . . . . . . . 12

NOTE: This module was developed as part 

of the series “Investigating the Climate 

System.”The series includes five modules: 

developed under one series title, they
 Appendix E: TRMM Introduction/Instruments . . . . . . . . . . . . . . . . 19

were designed so that each module could


. . . . . . . . . . . . . . . . . . . . . . . . . . . 21

downloaded at:


be used independently. They can be freely
 Appendix F: Florida Weather Page 

Clouds, Energy, Precipitation, Weather,


and Winds. While these materials were
 Appendix D: Problem-Based Learning . . . . . . . . . . . . . . . . . . . . . . . 17

http://www.strategies.org/CLASS.html
 Appendix G: Cloud Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

June 2003 

CONTENTS 

Grade Levels; Time Required; Objectives;


Disciplines Encompassed; Key Terms; Key Concepts . . . . . . . . . . . . 2

Suggested Reading/Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Truth Revealed after 200 Years of Secrecy! 

Pre-Activity; Activity One; Activity Two;


Activity Three; Extensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Part 2: How is the intensity and distribution 

Airplane Pilot or Movie Critic? 

Part 3: How can you study rain? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Foreseeing the Future of Satellites! 

online, go to:


https://ehb2.gsfc.nasa.gov/edcats/
 Activity Three; Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Appendix B: Assessment Rubrics & Answer Keys. . . . . . . . . . . . . . 13

Appendix C: National Education Standards. . . . . . . . . . . . . . . . . . . 15

Appendix H: Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

1 Investigating the Climate System: PRECIPITATION 
Investigating the Climate System 

Precipitation Precipitation


“The Irrational Inquirer” 

GRADE LEVELS 

Grades 5–8 

TIME REQUIRED 

Ten to twelve 45-minute class periods 

OBJECTIVES 

● Students will analyze data and interpret information 

in order to make predictions. 

● Students will utilize satellite data to determine the 

intensity and distribution of rainfall. 

● Students will apply satellite data to improve the 

safety of air travel. 

● Students will analyze and research global rainfall 

patterns. 

● Students will apply various scientific methods 

in order to collect and interpret precipitation 

measurements. 

● Students will apply various scientific methods in 

order to predict precipitation events. 

● Students will examine long-range weather predictions and compare them to archival satellite data. 

● Students will study scientific data to determine how 

rainfall intensity and temperatures change vertically 

as well as horizontally. 

● Students will investigate the effectiveness of using 

the traditional scientific method in meteorological 

research. 

● Students will use their knowledge of TRMM to propose new instruments and satellite missions, which 

will aid us in understanding and predicting changes 

in the Earth’s climate. 

● Students will present their ideas to the class. 

DISCIPLINES ENCOMPASSED 

Meteorology, climatology, geography, language arts, 

mathematics (data analysis, graphing skills), and 

atmospheric science 

KEY TERMS 

active sensor 

bright band 

climate 

climatology


coalesce


condensation nuclei/cloud nuclei


dew point/humidity


graupel


hail


latent heat


meteorology


passive sensor/radiometer


radar


radiation


rainfall intensity/rainfall rate


scientific method


Sun synchronous


supercooled water


total integrated rainfall rate


total ozone concentration


turbulence


weather 


KEY CONCEPTS 

● Clouds that produce thunderstorms, and therefore 

heavy rain and hail, are called cumulonimbus. These 

clouds often span an extremely large temperature 

range. In strong thunderstorms, where the updrafts 

exceed 10 m/s, raindrops can actually be lofted up 

above the freezing level (where the temperature is 

lower than 0°C). Some of these drops freeze to produce ice particles, while others remain in liquid 

form despite the below-freezing temperatures— 

these are called supercooled water droplets. The 

combination of liquid and ice above the freezing 

level is known as the “mixed-phase layer.” In this 

region of the cloud, the ice particles and liquid 

water drops are colliding with each other. As a liquid drop collides with an ice particle, the liquid 

attaches, or accretes, to the ice, enlarging the size of 

the ice particle. Eventually, the ice particle with 

accreted liquid water (known as graupel) falls out 

of the updraft either because the updraft is weakening in that part of the cloud or the particle 

becomes too heavy. In some instances where the 

updraft in the cloud is tilted with height, the particle can actually fall back into the main part of the 

2 Investigating the Climate System: PRECIPITATION 
updraft lower down in the cloud. The particle may 

then be swept back up into the mixed-phase 

region, and grow again by accretion. If this process 

occurs a number of times, the graupel grows to 

become what we call hail. 

● As the snow crystals in cumulonimbus clouds fall 

and get close to the 0°C region, they stick together 

and become large collections, or aggregates, of 

snow crystals. Subsequently, as they continue to fall, 

they start to melt so that a ring of liquid water forms 

around the aggregate. Because liquid water reflects 

much more energy back to the radar compared to 

ice, and because it only takes a small coating of liquid water for the aggregate to look like a raindrop 

to the radar, the radar senses that it is seeing really 

big drops. This is what produces the radar bright 

band (melting aggregates of snow flakes). As the 

particles continue to fall below the bright band, the 

large aggregate eventually melts into a large raindrop which, because of aerodynamic drag, eventually breaks up into smaller drops—which reduces the 

amount of power returned to the radar. The bright 

band layer shows up clearly on TRMM radar images. 

● An advantage of TRMM over other satellites is its 

ability to use radar to penetrate through clouds, 

providing scientists with the three-dimensional 

structure of the rain formation. This is important 

since it is the distribution of latent heat within 

clouds that affects the large-scale circulations of the 

atmosphere. Recall that latent heat is released when 

water changes phase: vapor to liquid and liquid to 

solid. Depending on the strength of the updraft and 

other properties of the surrounding atmosphere, 

different clouds may release latent heat at different 

heights in the atmosphere. Forecast models need 

this information on the distribution of latent heat 

(inferred from radar structure) to accurately predict 

weather. 

PREREQUISITE KNOWLEDGE 

PART 1 

How satellites observe weather and other 

phenomena from space 

According to Dr. John Theon, initiator and former program scientist for the TRMM satellite,“There are atlases 

of average monthly, seasonal, and annual rainfall over 

much of the Earth (except in the frozen regions of the 

planet) measured by (satellites’) passive sensors. 

Because it is necessary to make assumptions about 

the size, density, and shape of the particles, as well as 

the amount of emission coming from only the clouds, 

these sensors provide a very indirect measure of precipitation. Also, passive sensors can infer only the total 

accumulated depth of precipitation in the cloud, not 

its vertical structure. The unique aspect of the TRMM 

satellite is that it utilizes passive instruments as well as 

active instruments which can see the full vertical 

structure of precipitation in the cloud, thus providing 

more accurate rainfall measurement. 

“There are many other climatically important measurements obtained from satellites, such as the vertical 

temperature structure of the atmosphere, sea surface 

temperature and wind, total ozone concentration, 

ocean productivity, and land biomass. These data are 

available from NASA and NOAA (National Oceanic & 

Atmospheric Administration). 

“The TRMM orbit limits its measurements to latitudes 

between 35°N and 35°S. TRMM does not acquire observations at higher latitudes. There are no other direct 

measurements of rainfall from satellites as accurate as 

TRMM. There are several military satellites with passive 

sensors that observe every place on Earth two times 

each day, but because they are in Sun synchronous 

orbits, they measure rain at the same local time at each 

place each day, a poor way to observe rain. Since rainfall occurs in highly variable patterns, observations at 

each place should be made at various times throughout the day, as is done by TRMM. Also, passive sensors 

measure only the total integrated rainfall rate, but 

radars (like those on TRMM) can measure the vertical 

profile of rain, which is important for understanding 

where the rain is forming, whether it is reaching the 

ground, and its effects on the stability and circulation 

of the atmosphere.” 

How passive sensors (microwave radiometers) and 

active sensors (radars) work 

A passive sensor (a radiometer) simply receives and 

measures the energy emitted by its target objects 

(raindrops, in this case); TRMM radiometers are also 

sensitive to the energy emitted by the ocean/land surface, water vapor in the atmosphere, and scattering by 

ice particles. An active sensor (a radar, in the case of 

TRMM) transmits energy and measures how much of 

that energy is reflected back from the target objects. 

Any object whose temperature is greater than 

absolute zero emits energy. 

3 Investigating the Climate System: PRECIPITATION 
Description of TRMM satellite image: 

Hurricane Trail 

In the image above, the passing storm creates surface 

turbulence that stirs up cooler water from below the 

surface of the sea. Had weather forecasters been able 

to see through the clouds, using TRMM satellite data, 

which most other satellite sensors are unable to do, 

they would have been able to see the relatively cool 

sea surface temperatures in the wake of Hurricane 

Mitch—and predict that the second hurricane would 

weaken, because of the lack of warm water, and thereby become less of a threat to the regions in its path. 

A more accurate forecast might have prevented 

unnecessary evacuations and certainly calmed fears. 

PART 2 

● How temperature changes with varying height in 

the atmosphere. 

● How to read TRMM data. 

● TRMM’s ability to “see” through clouds has important implications, not only in understanding weather, but also in helping pilots navigate through dangerous clouds. 

● Ice and rain emit and reflect microwave energy differently. The TRMM satellite provides scientists with 

images that show these differences. 

● TRMM is the only satellite that provides images 

showing the vertical structure of rain. 

● Supercooled water can remain in liquid form at 

temperatures as low as –40°C if there are no cloud 

nuclei (condensation nuclei) upon which to coalesce. As it passes through supercooled water 

droplets, an airplane may serve as the nucleus for 

condensation such that supercooled water will 

immediately freeze on contact with the surface of 

the aircraft. Because ice can weigh down the plane 

and alter its aerodynamic characteristics, the consequences can be catastrophic . 

● Rainfall intensity (rainfall rate) is measured by 

TRMM for various locations and times. Many such 

observations must be averaged for each area over a 

period of time to obtain a reasonable estimate of 

the total rain amount. Studies have shown that this 

is a valid technique of estimation. Maps of rainfall 

rates averaged over various time periods (say a 

month, a season, or a year) can then be developed. 

PART 3 

● The Scientific Method 

The scientific method is a series of steps that are 

used in scientific investigations in order to test a 

hypothesis. There are typically four steps: 

1. Observe and describe a specific phenomenon. 

2. Develop a hypothesis that explains what you 

have observed. 

3. Make predictions based on this hypothesis. 

4. Test those predictions by experimentation/observation; modify hypothesis based on results, if 

necessary. 

● The next research mission to advance satellite observations of rainfall is called the Global Precipitation 

Mission (GPM), now under study by NASA’s Earth 

Science Enterprise. It will consist of up to eight small 

satellites, each carrying a passive microwave sensor 

to observe rainfall, plus a single “flying rain gauge,” a 

larger “mother” satellite that will carry a precipitation 

radar to aid in calibrating observations from the 

smaller satellites. This group of nine satellites will be 

launched into polar orbits from which rainfall can be 

observed every three hours anywhere on Earth. The 

space agencies of Japan, China, Taiwan, Europe, and 

Brazil have expressed interest in participating in this 

mission. The GPM satellites will be in a slightly higher orbit than TRMM. At an altitude of 350 km, TRMM 

was able to use a smaller, less expensive antenna. 

The new series of satellites will be launched into 

orbits that are about 450 km above the Earth. 

Although the antennas will have to be larger and 

more expensive, the lower drag at higher altitudes 

will slow the rate of decay of the orbit, allowing the 

satellites to stay in orbit longer, possibly 5–10 years. 

(TRMM was designed to last a minimum of three 

years, but is now expected to last 5–6 years.) 

4 Investigating the Climate System: PRECIPITATION 
ADDITIONAL PREREQUISITE KNOWLEDGE 

AND FACTS 

● Chart reading skills 

● Understanding of mean, median, and mode 

● Water cycle 

● Supercooled water droplets remain liquid from 0°C 

to as low as –40°C if there are no cloud nuclei upon 

which to freeze. 

● Map reading skills 

● The first record of rain measurements occurred in 

India in 350 B.C. 

● The first use of rain gauges occurred in 1247 in 

China. (See “Major Milestones in the History of 

Precipitation Research” on page 11 of A Global Eye 

on Tropical Rainfall Measuring Mission [TRMM] for 

more rainfall measurement facts.) 

● Every year, The Old Farmer’s Almanac makes a general weather forecast for the United States as a whole, 

as well as 16 regional weather forecasts. It predicts 

weather information for each month. For example, 

in 1998 it predicted: “Texas, January 1999: 

Temperature 47° (2° above average); precipitation 0.5” 

(1” below average). 1–9 Sunny, mild. 10–20 Sunny, cool. 

21–31 Snow north, rain central, warm south.” There is 

no scientific basis for such predictions other than 

historical records which have skill only in the gross 

climatic sense. 

● For the teacher—Activity One: Scientific Method 

(p.10)—The purpose of this activity is for students 

to think about the scientific method and how it 

applies to studying real-world Earth systems. The 

traditional application of the scientific method, 

involving experiments in controlled environments, 

is not possible in this type of research. There are no 

independent/dependent variables and there is no 

way to repeat an experiment to test conclusions. 

5-Year TRMM Climatology January 1998–December 2002 

SUGGESTED READING/RESOURCES 

Forpe, Will, editor. 1977. The Best of The Old Farmer’s 

Almanac. New York: Jonathan David Publishers. 

Lauber, Patricia. 1990. Seeing Earth from Space. New 

York: Orchard Books. Overview of how satellites 

collect data. 

Ludlum, David. 1976. The Country Journal New England 

Weather Book. Boston: Houghton Mifflin. 

The Old Farmer’s Almanac. P.O. Box 520, Dublin, NH 

03444. Phone: 603-563-8111. Web site: 

www.almanac.com 

Cerullo, Mary. 2000. Ocean Detectives: Solving the 

Mysteries of the Sea (and Teacher’s Guide). Boston: 

Turnstone. 

Williams, Jack. 1997. The Weather Book. Vintage Books. 

TRMM Web Sites: 

http://trmm.gsfc.nasa.gov (main TRMM Web site, 

with Breaking News, Real-Time Data, and Maps of 

Falling Water: Three Years of TRMM Data) 

TRMM Hurricane Trail image—http://trmm.gsfc.


nasa.gov/images_dir/mitch.html


5-Year TRMM Climatology—http://trmm.gsfc.


nasa.gov/images/5-year_TRMM_climo.gif


Any additional, appropriate Web sites, such as: 

Aqua—http://aqua.nasa.gov 

Goddard Space Flight Center Questions of the Week 

http://www.gsfc.nasa.gov/scienceques2002/ 

20021004.htm 

National Oceanic and Atmosphertic Administration 

http://www.noaa.gov 

NASA’s Earth Observatory 

http://earthobservatory.nasa.gov/Newsroom 

The Weather Channel 

http://www.weather.com/index.html 

http://phyun5.ucr.edu/~wudka/Physics7/Notes_ 

www/node5.html 

http://teacher.nsrl.rochester.edu/phy_labs/ 

AppendixE/AppendixE.html 

5 Investigating the Climate System: PRECIPITATION 
PART 1 

How are rainfall rates measured? 

●	 How have we traditionally collected 

rainfall (and other weather) data? 

●	 How has that data been used to 

make forecasts? 

MATERIALS 

Street map of the local community 

2–3 sheets of clear acetate that will cover the map 

Computers with Internet connection 

Samples of The Old Farmer’s Almanac (optional, sample 

page provided in Appendix E), Florida, 1997 

Reference books on weather 

Truth Revealed After 200 Years of Secrecy! 

SETTING THE STAGE 

A

somewhat shady investigative reporter, Sheila 

Wright Jonque, is pursuing leads for an exposé 

to be published in the 

popular supermarket tabloid, The 

Irrational Inquirer. Because her 

newspaper has been sued several 

times for unsubstantiated stories 

written by Sheila, her editor now 

insists that she provide supporting evidence from an independent source before he’ll agree to 

publish any more of her articles. 

Sheila has found an unlikely (and 

unwilling) accomplice in the 

state climatologist. She wants the 

climatologist to dig up facts for 

her to corroborate a breaking 

story, the first in a series titled 

“How Do They Do That: 

Predicting Weather,” about the 

reliability of the venerable The 

Old Farmer’s Almanac. 

The Old Farmer’s Almanac has 

been predicting the weather 

since 1792. It uses past rainfall 

patterns and many other data in 

a secret formula to make forecasts up to a year and a half in 

advance. 

Sheila wants the state climatologist to help her document how 

well The Almanac’s past predictions of precipitation events have 

correlated with actual events (in 

other words, how often are their 

predictions correct?). 

To provide an introduction for 

her story, she first needs to 

describe how scientists collect 

rainfall and other weather data, 

in the past and present. She then 

needs to understand how they 

predict rainfall. With this information, she will be able to write 

her article. Because Sheila’s editor is hesitant to publish an article written by her, she needs 

your help, as the state climatologist, to ensure the information 

provided in her article is accurate. How would you help Sheila 

grasp the basics of meteorology 

so she can research her story? 

Where would you go to get her 

information to compare past and 

present weather information? 

About two weeks ago, Sheila 

took it upon herself to conduct 

an interview with Dr. John 

Theon, initiator and former 

Program Scientist for the TRMM 

satellite. The following is some 

information she obtained from 

him: 

Notes from an interview with 

Dr. John Theon on how satellites 

measure weather and other 

phenomena from space: 

“There are atlases of average 

monthly, seasonal, and annual 

rainfall over most of the Earth 

(except in the frozen regions of 

the planet) measured by (satellites’) passive sensors. These sensors do not directly measure 

frozen precipitation [e.g., snow], 

so they cannot provide truly 

global precipitation observations. 

(Although the TRMM radar cannot detect most snow, passive 

sensors are sensitive to the scattering from ice particles). There 

are average monthly, seasonal, 

and annual global surface temperature observations made by 

satellite sensors. There are also 

average cloud cover observations 

over the entire Earth obtained 

from satellites. 

6 Investigating the Climate System: PRECIPITATION 
Part 1: How are rainfall rates measured? 

“There are many other climatically important measurements obtained from satellites, such as the 

vertical temperature structure of 

the atmosphere, sea surface temperature and wind, total ozone 

concentration, ocean productivity, and land biomass. These data 

are available from NASA and 

NOAA.” 

“The TRMM (Tropical Rainfall 

Measuring Mission) orbit limits 

its measurements to latitudes 

between 35°N and 35°S. There 

are no other measurements of 

rainfall from satellites as accurate 

as TRMM. There are several military satellites with passive sensors that cover every place on 

Earth two times each day, but 

because they are in Sun synchronous orbits, they measure rain at 

the same local time at each place 

each day, a poor way to observe 

rain (since rain is notoriously 

chaotic in its day-to-day occurrence). TRMM is an asynchronous orbit, meaning that it 

observes a given place at varying 

times of the day each month. 

Also, passive sensors measure 

only the total integrated column 

rainfall rate (the sum of all rain 

in the atmospheric column—not 

just what’s hitting the ground), 

but radars (like those on TRMM) 

can measure the vertical profile 

of rain which is important for 

understanding where the rain is 

forming.” 

“Meteorologists sometimes estimate area rainfall from groundbased radar observations (actually, the national weather service 

uses radar whenever possible), 

but the weather radars are sometimes so poorly calibrated that 

these estimates are not very accurate. However, calibration is only 

a small part of the problem. 

There are many difficulties in 

using radar to estimate the actual 

rainfall on the ground; and this 

includes measurements from the 

TRMM PR (Precipitation Radar). 

Because the radar measures 

above the ground surface and 

drops can evaporate before they 

hit the ground, not all of the 

radar beam may be sampling 

inside of the cloud. Part may be 

outside, and most importantly, 

the distribution of raindrops 

varies from one location to 

another, as well as from one time 

to another. Since radars have to 

make assumptions about the distribution of raindrops in the 

clouds, which are often incorrect, the rainfall estimates are 

often way off compared to rain 

gauges. This brings up another 

problem—the spatial variability 

of rain and the sampling of a rain 

gauge (point measurement) vs. 

the large area sampled by a radar 

(see the next paragraph below). 

TRMM’s Precipitation Radar (PR), 

on the other hand, is the best 

calibrated, most stable radar in 

the world! In addition, PR’s viewing geometry is far superior to 

that of ground-based radars. By 

the way, radar is termed an active 

sensor, not a passive one.” 

“Meteorologists use groundbased rain gauges, usually located at weather stations, to measure rainfall. Rain gauge measurements are not necessarily representative of rainfall amount over 

a general area (as inferred from 

radar), since rainfall amount is 

highly variable from place to 

place, even across short distances. TRMM measures rain 

averaged over a whole area. 

Consider that a radar samples an 

area 105

–106 times larger than 

that of a rain gauge; if the precipitation varies on a scale smaller 

than what the radar can sample, 

the radar estimate will be biased. 

On the other hand, radar does 

give a better picture of the area 

coverage of rain compared to 

rain gauges.” 

A good math problem for the 

students would be to calculate 

how much bigger an area the 

radar samples, compared to 

that of a rain gauge. Figure 

that a rain gauge has an area 

of 0.1m and that the radar 

samples an area of about 1 km 

x 1 km. 

“It is certainly true that The Old 

Farmer’s Almanac uses historical 

data to predict the coming year’s 

weather. This will be a good forecast if the weather follows previous averages. However, there is 

little forecast information in historical averages if the weather is 

not typical. Weather is a very 

noisy variable, meaning that averages do not describe it well 

except in general terms. Yes, in 

general, it is colder in winter 

than in summer, and yes, The 

Almanac sometimes forecasts a 

storm accurately well in advance, 

but this is more by chance than 

by skill. Even the best scientific 

forecasts for more than a week 

or 10 days in advance have only 

a 10 percent skill, and the best 

forecasters will tell you that.” 

7 Investigating the Climate System: PRECIPITATION 
Part 1: How are rainfall rates measured? 

PRE-ACTIVITY 

● Determine how you would make a rain gauge. 

Collect the materials, make the gauge, set it up in 

your backyard, and write down your measurements 

in a log. Be sure to include the date and time of 

each observation. 

● After each member of the class marks the location 

of his or her home on a street map of the community, cover it with clear acetate and make a map of 

rainfall amounts. What is the most effective way to 

show the information on the map? Look for differences in the amounts of rainfall. Can you think of 

any factors related to environment or landscape 

that may cause variations? Discuss your findings, 

considering the statements made by Dr. Theon. 

Activity One: How are rainfall rates measured? 

As the state climatologist, your job is to help Sheila 

with her research for her article. Sheila is unfamiliar 

with the topic of meteorology, so she has requested 

that you help her in her background investigation. She 

needs information on different methods of measuring 

rainfall. Determine what information Sheila will need 

to conduct her research. Where would you, as the state 

climatologist, go to get this information? What information would you provide to her? Remember that 

Sheila is required to provide supporting evidence for 

her article, so include resources used in the 

investigation. 

Further Discussion Question 

Besides precipitation, other instruments also measure 

temperature, air pressure, humidity, and wind flow. 

How might these help forecast rainfall/precipitation? 

ActivityTwo: How are rainfall rates predicted? 

In writing her article, Sheila has found she needs additional information on the following topics. First determine where you would get this information. Then conduct your research and determine what information to 

give Sheila. 

● How is data collected and used to measure precipitation? Be sure to include information on satellites 

and The Old Farmer’s Almanac. 

● What are ground observations, weather records, and 

satellite observations, and what types of data do 

each provide? 

● How can people use this information to predict 

rainfall? 

Activity Three: Conclusion 

Sheila has decided that for her to determine the reliability of The Old Farmer’s Almanac, she will need to compare data from The Almanac with data collected from 

other resources. What kind of data would you look for? 

Where would you go to obtain this information? 

Once you’ve obtained the appropriate data, analyze 

and interpret the information for Sheila. What does it 

mean? 

Help Sheila write her article using the information you 

have gained. Is The Old Farmer’s Almanac accurate? 

Explain. 

LANGUAGE ARTS EXTENSION 

Each student should contribute a feature to produce a 

class edition of The Old Farmer’s Almanac. Examine a 

copy and choose one section that you would write for 

the next issue. 

MATH EXTENSION 

The Almanac gives the time of sunrise in Boston, 

Massachusetts. Use the Time Correction Tables to find 

the sunrise and sunset times (using Length of Day 

information) in your area. 

STATISTICS EXTENSION 

Explain what the evidence indicates about the reliability of The Old Farmer’s Almanac. The state climatologist, 

who supplied the satellite data, warns Sheila that she 

really should examine more data before she writes her 

story. Sheila’s never used data before, so she thinks a 

few examples are more than enough to satisfy her editor and the newspaper’s legal department. Discuss 

what you would consider to be a reliable sample size 

and how sample size affects students’ inferences. Use 

an example from the class; pick some characteristic 

that three students have in common (such as, last 

names beginning with S, or blue eyes) and then 

extrapolate that to represent the whole class. Is that 

extrapolation accurate? 

8 Investigating the Climate System: PRECIPITATION 
PART 2 

How is the intensity and distribution of rainfall determined? 

MATERIALS ● Temperature and rainfall 

vary at various altitudes.	 Line drawing of cloud diagram (reproducible for students to write 

on—see Appendix G); pencil and paper; Internet access 

Airplane Pilot or Movie Critic? 

SETTING THE STAGE 

A

private airplane was 

descending slowly 

toward an airport when 

it suddenly went into a 

steep dive, much to the 

dismay of its passengers and 

crew. After several minutes of 

terror, the pilot was able to 

regain control and safely land 

the plane. 

As luck would have it, it was a 

private jet carrying rock star 

Damonna and her latest fiancé. 

According to friends of the rock 

diva, the pilot left the cockpit 

unattended while he joined his 

celebrity passengers to watch 

the in-flight movie, “Airplane!” 

However, the pilot claims that 

he was at the controls throughout the flight and that the plane 

flew through an ice storm at 

30,000 feet. The ice coated the 

wings, he said, making the 

plane so heavy that it started to 

fall rapidly. According to the 

pilot, warming temperatures at 

lower altitudes melted enough 

ice that he was able to regain 

control of the plane and land it 

safely. 

Sheila Wright Jonque, investigative reporter for The Irrational 

Inquirer, has chosen this as the 

second story in her series “How 

Do They Do That: Predicting 

Weather.” In her interviews with 

the pilot and the passengers, 

she has found discrepancies in 

their statements. Sheila has 

asked the state climatologist to 

help her obtain data from the 

TRMM satellite to use in an 

attempt to reconstruct the 

entire event. 

In his interview with Sheila, the 

pilot claims to have hit turbulence at 30,000 feet as he 

descended through the clouds. 

He states that it was at this time 

that they passed through an 

area of supercooled water causing ice to form on the wings, 

subsequently causing the plane 

to drop 3,000 feet/minute. After 

less than a minute, he says, the 

plane reached the bottom of 

the bright band and the ice 

melted, allowing him to regain 

control, descend at a normal 

rate of 1,000 feet/minute, and 

safely land the plane. 

Can the climatologist back up 

the pilot’s claim by examining 

TRMM satellite data for that 

date over the region where the 

plane was flying? 

Activity One: What are we talking about? 

Before conducting any more research, Sheila has realized that she doesn’t fully understand the information 

she has gathered. As the state climatologist, she has 

asked you to brief her to bring her up to speed. Put 

together a briefing for her, including all relevant background information that will help her reconstruct the 

event and write the story. 

Activity Two: What happened? How do you find 

out if the pilot is telling the truth? 

Sheila has asked you to help research the information 

necessary to determine whether the pilot is telling the 

truth. She has determined three areas she needs help 

in. Is her list below complete? If not, what other information does she need? 

● The interior structure of clouds and how they form, 

● A description of the bright band, and 

● The importance of this information in flight 

navigation. 

Once you are done with the research, make a diagram 

for Sheila that shows how the incident might have 

happened. 

9 Investigating the Climate System: PRECIPITATION 
PART 3 

How can you study rain? 

Foreseeing the Future of Satellites! 

SETTING THE STAGE 

F

or her final article in 

her “How Do They 

Do That: Predicting 

Weather” series, 

Sheila Wright Jonque, investigative reporter, is trying to 

determine what the next er satellites, such as the 

generation of weather- TRMM satellite, and the 

observing satellites might be. types of questions scientists 

As the state climatologist, would like to be able to 

you’ve been asked for your answer in the future. 

help in understanding the 

capabilities of current weathActivity One: The Scientific Method 

a.	 You have worked with Sheila before and are aware 

that she is unfamiliar with the scientific method. 

Before she continues with this investigation, you 

would like to teach her about the scientific 

method, so she can use it to research, understand, 

and write her stories. What information do you 

need to provide for Sheila? 

b.	 How applicable is this method to real-world 

research in meteorology? 

c.	 Determine how meteorologists apply the scientific 

method to their real-world research. Are there differences between the scientific method in laboratory versus real-world conditions? Describe these 

differences. 

Activity Two: Why do we care about rainfall? 

MATERIALS 

● Internet access 

● Map of the world—highlight the area of TRMM 

coverage (provide two maps for each group of 

students working together) 

The central question that TRMM seeks to answer is 

“What is the global pattern of rainfall?” 

Observing and modeling the distribution of clouds 

and precipitation is important. Small changes in distribution can lead to big changes in climate, although 

we still don’t fully understand how and why. For 

instance, changing the average base height of clouds 

around the globe by 1000 feet would change the 

global climate. 

a.	 Sheila has spoken with a sociologist (someone who 

studies human society), who believes she should 

include information on the impact of rainfall patterns on human population in her article. As a climatologist, you are familiar with the effects of rainfall patterns. What information do you need to provide Sheila? Why is this important for her article? 

b.	 Working in small groups, study the two world maps 

depicting TRMM coverage. Look at the data presented. What information is provided? Discuss what 

you see, and any correlation between the data. Why 

did scientists choose the area of TRMM coverage 

that they did? 

c.	 How does the information you have just gathered, 

both the effects of rainfall patterns on human population and the data presented by the TRMM maps, 

relate to each other? 

10 Investigating the Climate System: PRECIPITATION 
Part 3: How can you study rain? 

Activity Three: Future Studies 

a.	 In investigating the future of weather studies, you 

and Sheila are working together to determine what 

questions scientists will need to answer. What background information do you need to know? What 

questions have scientists already answered? What 

information would help meteorologists or climatologists make better short and long-range forecasts? 

What instruments would be needed to collect this 

data? 

b.	 What do you think Sheila’s final article should be 

titled? What information would you recommend 

Sheila include? 

SCIENCE EXTENSION 

It is your task to invent the next generation of weather-observing satellites. Working in small groups, write 

up a description of your satellite and what questions it 

will answer, so that Sheila can use the information to 

write her story. After the groups’ ideas have been presented, as a class, choose three frequently mentioned 

questions that need to be answered about rainfall and 

its impact on human society. 

SCIENCE/ART EXTENSION 

Use drafting paper to draw a design of an instrument 

or what the next generation of weather-observing 

satellites might look like. 

UNIT EXTENSIONS 

Language Arts, Fine Arts, and Foreign Language 

Write up the conclusions of one of these problems 

using one of these styles: 

●	The National Inquirer: Instead of quoting the subject, 

write,“Friends say...”Vary the type style and point 

size. Write short sentences with many exclamation 

points. 

●	The Wall Street Journal: Reference scientific studies, 

quote authoritative experts—real or imagined— 

from government and business. Use big words and 

small type. 

● A comic book: Use lots of artwork. 

●	Any periodical from another country, such as 

France or Spain. Write in the native language of 

that country. 

Science/Geography Extension: Sheila Is Missing! 

Colleagues at the newspaper have heard rumors that 

the editors were trying to get rid of Sheila. Perhaps, 

they wonder, was she abducted by a band of Amazon 

headhunters? They may be correct, because Sheila has 

not been heard from since she sent an undated report 

that torrential rains were assaulting the coastal region 

around the mouth of the Amazon River. She managed 

to report back that average rainfall for the month 

exceeded 20 inches. Examine the TRMM monthly rainfall data and find any months where the mean rainfall 

exceeded 20 inches at the mouth of the Amazon River. 

When was the last time she could have been heard 

from? 

trmm.gsfc.nasa.gov/images_dir/avg_rainrate.html 

11 Investigating the Climate System: PRECIPITATION 
APPENDIX A 

Bibliography/Resources 

Forpe, Will, editor. 1977. The Best of The Old Farmer’s 

Almanac. New York: Jonathan David Publishers. 

Lauber, Patricia. 1990. Seeing Earth from Space. New 

York: Orchard Books. Overview of how satellites collect data. 

Ludlum, David. 1976. The Country Journal New England 

Weather Book. Boston: Houghton Mifflin. 

The Old Farmer’s Almanac. P.O. Box 520, Dublin, NH 

03444. Phone: 603-563-8111. Web site: 

www.almanac.com 

Cerullo, Mary. 2000. Ocean Detectives: Solving the 

Mysteries of the Sea (and Teacher’s Guide). Boston: 

Turnstone. 

Williams, Jack. 1997. The Weather Book. Vintage Books. 

Web Sites: 

TRMM 

http://trmm.gsfc.nasa.gov 

Aqua 

http://aqua.nasa.gov 

Goddard Space Flight Center Questions of the Week 

http://www.gsfc.nasa.gov/scienceques2002/ 

20021004.htm 

National Oceanic and Atmospheric Administration 

http://www.noaa.gov 

NASA’s Earth Observatory 

http://earthobservatory.nasa.gov/Newsroom 

The Weather Channel 

http://www.weather.com/index.html 

Journals: 

AMS Newsletter, published by the American 

Meterological Society 

The Earth Scientist, published by the National Earth 

Science Teachers Association 

Geotimes, published by the American Geological 

Institute 

GSA Today, published by the Geological Society of 

America 

Journal of Geography, published by the National 

Council for Geographic Education 

Journal of Geoscience Education, published by the 

National Association of Geoscience Teachers 

Nature, Macmillan Publishers 

Science, published by the American Association for the 

Advancement of Science 

Scientific American 

Weatherwise, Heldref Publications 

12 Investigating the Climate System: PRECIPITATION 
APPENDIX B 

Assessment Rubrics & Answer Keys 

Rubric: PARTS 1, 2, 3 

SKILL Extensively Frequently Sometimes Rarely 

Demonstrates ability to access relevant 

information at appropriate Internet sites 

Collects/organizes data 

Represents findings clearly on map/graph 

or written/oral explanation 

Participates in class discussions/ 

presentations 

Infers links between topic under 

investigation and weather/climate 

13 Investigating the Climate System: PRECIPITATION 
Appendix A: Assessment Rubrics & Answer Keys 

icing of plane 

°C 

°C 

end of hail formation 

end of icing 

hail 

hail 

GROUND °C 

30,000 ft. 

50,000 ft. 

25,000 ft. 

temp: -10

15,000 ft. 

temp: 0

turbulence 

supercooled water 

cloud base: dew point 

bright band: freezing layer 

rain in clouds 

rain 

temp: 20

Cloud Diagram Answer Key: PART 2 

Airplane Pilot or Movie Critic? If the plane dropped 3,000 feet/minute after ice formed on 

the wings at 30,000 feet, the plane would reach the end of the bright band (at 15,000 feet) in 5 

minutes. The pilot claims it took less than a minute to reach the end of the bright band—therefore, 

the pilot was lying about how long it actually took him to regain control of the plane! 

14 Investigating the Climate System: PRECIPITATION 
APPENDIX C 

National Education Standards 

SCIENCE 

Content Standard: K–12 

Unifying Concepts and Processes 

Standard: As a result of activities in grades K–12, all 

students should develop understanding and abilities 

aligned with the following concepts and processes: 

● Systems, order, and organization 

● Evidence, models, and explanation 

● Constancy, change, and measurement 

Content Standards: 5–8 

Science as Inquiry 

Content Standard A: As a result of activities in grades 

5–8, all students should develop: 

● Abilities necessary to do scientific inquiry 

● Understandings about scientific inquiry 

Physical Science 

Content Standard B: As a result of activities in grades 

5–8, all students should develop an understanding of: 

● Properties and changes in properties of matter 

● Transfer of energy 

Earth and Space Science 

Content Standard D: As a result of activities in grades 

5–8, all students should develop an understanding of: 

● Structure of the Earth system 

Science and Technology 

Content Standard E: As a result of activities in grades 

5–8, all students should develop: 

● Understandings about science and technology 

Science in Personal and Social Perspectives 

Content Standard F: As a result of activities in grades 

5–8, all students should develop an understanding of: 

● Personal health 

● Natural hazards 

● Science and technology in society 

National Research Council. 1996. National Science Education 

Standards p. 115, 143–171. Washington, DC: National Academy Press. 

MATH 

Curriculum Standards for Grades 5–8 

Standard 1: Mathematics as Problem Solving 

Standard 2: Mathematics as Communication 

Standard 3: Mathematics as Reasoning 

Standard 4: Mathematical Connections 

Standard 10: Statistics 

Standard 13: Measurement 

National Council of Teachers of Mathematics. 1989. Curriculum and 

Evaluation Standards for School Mathematics p. 63–119. Reston, VA: 

The National Council of Teachers of Mathematics, Inc. 

GEOGRAPHY 

National Geography Standards for Grades 5–8 

The World in Spatial Terms 

Standard 1: How to use maps and other geographic representations, tools, and technologies to 

acquire, process, and report information from a 

spatial perspective. 

Standard 3: How to analyze the spatial organization 

of people, places, and environments on Earth’s 

surface. 

Physical Systems 

Standard 7: The physical processes that shape the 

patterns of Earth’s surface. 

Human Systems 

Standard 11: The patterns and neworks of economic interdependence on Earth’s surface. 

Environment and Society 

Standard 15: How physical systems affect human 

systems. 

American Geographical Society, Association of American Geographers, 

National Council for Geographic Education, and National Geographic 

Society. 1994. Geography for Life: National Geography Standards 

p. 143–182. Washington, DC: National Geographic Research and 

Exploration. 

15 Investigating the Climate System: PRECIPITATION 
Appendix B: National Education Standards 

ENGLISH LANGUAGE ARTS 

Standard 1: Students read a wide range of print and 

nonprint texts to build an understanding of texts, of 

themselves, and of the cultures of the United States 

and the world; to acquire new information; to respond 

to the needs and demands of society and the workplace; and for personal fulfillment. Among these texts 

are fiction and nonfiction, classic and contemporary 

works. 

Standard 3: Students apply a wide range of strategies 

to comprehend, interpret, evaluate, and appreciate 

texts. They draw on their prior experience, their interactions with other readers and writers, their knowledge of word meaning and of other texts, their word 

identification strategies, and their understanding of 

textual features (e.g., sound-letter correspondence, 

sentence structure, context, graphics). 

Standard 4: Students adjust their use of spoken, written, and visual language (e.g., conventions, style, 

vocabulary) to communicate effectively with a variety 

of audiences and for different purposes. 

Standard 5: Students employ a wide range of strategies as they write and use different writing process 

elements appropriately to communicate with different 

audiences for a variety of purposes. 

Standard 6: Students apply knowledge of language 

structure, language conventions (e.g., spelling and 

punctuation), media techniques, figurative language, 

and genre to create, critique, and discuss print and 

nonprint texts. 

Standard 7: Students conduct research on issues and 

interests by generating ideas and questions, and by 

posing problems. They gather, evaluate, and synthesize 

data from a variety of sources (e.g., print and nonprint 

texts, artifacts, people) to communicate their discoveries in ways that suit their purpose and audience. 

Standard 8: Students use a variety of technological 

and informational resources (e.g., libraries, databases, 

computer networks, video) to gather and synthesize 

information and to create and communicate 

knowledge. 

Standard 12: Students use spoken, written, and visual 

language to accomplish their own purposes (e.g., for 

learning, enjoyment, persuasion, and the exchange of 

information). 

National Council of Teachers of English and International Reading 

Association. 1996. Standards for the English Language Arts p. 24–46. 

Urbana, Illinois and Newark, Delaware: National Council of Teachers of 

English and International Reading Association. 

SOCIAL STUDIES 

Strand 3: People, Places, and Environments. Social 

Studies programs should include experiences 

that provide for the study of people, places, and 

environments. 

Strand 8: Science, Technology, and Society. Social 

Studies programs should include experiences that 

provide for the study of relationships among science, 

technology, and society. 

National Council for the Social Studies. 1994. Expectations of 

Excellence: Curriculum Standards for the Social Studies p. 19–30. 

Washington, DC: National Council for the Social Studies. 

16 Investigating the Climate System: PRECIPITATION 
APPENDIX D 

Problem-Based Learning 

What is Problem-Based Learning? 

T

he Problem-Based Learning (PBL) model of teaching is a lot like it sounds; students learn by solving 

a problem. While this occurs in all classrooms to a 

different extent, the PBL learning model causes a drastic shift in the roles of students and teachers. In traditional teaching methods, the teacher acts as director 

of student learning, which is commonly passive. With 

PBL, these roles shift. Students become active and 

responsible for their own learning, and the activity is 

student-centered; the teacher becomes more of a 

facilitator or guide, monitoring student progress. 

By using this model, the students gain information 

through a series of self-directed activities in which the 

students need to solve a problem. These problems 

drive the learning process and are designed to help 

students develop the skills necessary for critical thinking and problem solving. Students learn that in the 

real world, problems, and their solutions, are not 

always cut and dried, and that there may be different 

possible answers to the same problem. They also learn 

that as they continue to gain information, they need 

to readjust their plan. In other words, they must perform self-assessment. 

A PBL lesson starts with a problem posed directly to 

the students. These problems are poorly structured to 

reflect real world situations. Students (most commonly 

in small, cooperative groups) are then left to determine what steps need to be taken in order to solve the 

problem. The teacher does not give the students the 

information needed prior to the activity. However, the 

teacher does need to make sure the students have 

enough prior knowledge to be able to interpret the 

problem and determine a plan of action. 

A key component of PBL is constant feedback. While 

the students are constantly assessing their work, and 

in turn adjusting their plan, teachers also need to provide continual, immediate feedback. Without feedback, 

students may be uncomfortable with this type of 

activity, because they do not know what is expected of 

them. Teacher feedback provides reinforcement for 

student learning. Feedback should be an authentic, 

performance-based assessment. Students need to 

continually evaluate their contributions. Rubrics provide a good guide for both teachers and students, to 

ensure that the students are continually kept on the 

right track. 

Why use PBL? 

Traditional teaching methods focus on providing 

students with information and knowledge. The PBL 

model also adds “real world” problem-solving skills to 

the classroom. It teaches students that there is sometimes more than one possible answer, and that they 

have to learn how to decide between/among these 

answers. 

Students and PBL 

Students are broken up into groups and are presented with a poorly structured, complex problem. 

Students should have enough background knowledge 

to understand the problem, but should not be experts. 

Any one, specific solution to the problem should not 

be evident. The students will need to determine what 

the problem is that they need to solve. Some organizational questions they may ask themselves are: 

●	 What do we know about this problem? 

●	 What do we need to know? 

●	 How/where do we get the information needed to 

solve the problem? 

The next step for the students is to determine a 

problem statement. From the information given to 

them in the problem, they should determine what 

they need to know and then plan a course of action to 

get the information they need to propose a solution. 

In implementing this plan, they will have to gather 

information to help them solve the problem. They will 

need to be sure that the resources they use are current, credible, accurate, and unbiased. As information is 

gathered and interpreted, they then apply their new 

knowledge, reevaluate what they know, and redetermine what they need to know to solve the problem. 

Once all the information is gathered, interpreted, and 

discussed, the group works together to propose a final 

solution. 

17 Investigating the Climate System: PRECIPITATION 
Appendix D: Problem-Based Learning 

Benefits of PBL 

By using the Problem-Based Learning method, students gain more than just knowledge of facts. They 

develop critical thinking skills while working in collaborative groups to try to solve a problem. In doing this, 

they learn how to: 

●	 interpret the question/problem, 

●	 develop a problem statement, 

●	 conduct research, reevaluating prior knowledge as 

new knowledge is gained, 

●	 determine possible solutions, and 

●	 pick the best possible solution based on the information they have gathered. 

By providing immediate student feedback, the students can continually readjust their thinking, correcting any misconceptions or errors before moving on. 

By using PBL, students become more familiar with 

“real world” problems. They learn that there is not 

always only one correct answer, and that they need to 

work together to gather enough information to determine the best solution. 

The PBL Classroom 

When using the PBL model of instruction, it is best for 

students to work in small cooperative groups. The 

objective of this model is for students to work in a collaborative setting where they can learn social and ethical skills to determine how to answer the question 

presented. Students are expected to regulate themselves while in these working groups. 

PBL Assessment 

As the student groups work together to collect information, they will need to constantly assess their own 

progress and readjust their plan. As they do this, they 

will need continual, immediate feedback from the 

teacher. When they become more comfortable with 

this model, they will learn to rely less on the teacher 

and become more independent. By providing the students with the grading rubric, it will serve as a guide 

to ensure they are on the right track throughout the 

activity. 

18 Investigating the Climate System: PRECIPITATION 
APPENDIX E 

TRMM Introduction/Instruments 

Introduction to the Tropical Rainfall 

Measuring Mission (TRMM) 

R

ainfall is one of the most important weather and 

climate variables that determine whether 

mankind survives, thrives, or perishes. Water is so 

ubiquitous on planet Earth that we often take it for 

granted. Too much water results in devastating floods, 

and the famine caused by too little water (drought) is 

repsonsible for more human deaths than all other natural disasters combined. Water comprises more than 

75 percent of our bodies and as much as 95 percent of 

some of the foods we eat. 

Water is essential to life, as it nourishes our cells and 

removes the waste they generate. Water determines 

whether plants produce food, or whether they wither 

from drought or rot from dampness. Water is essential 

to our homes and factories, to our production of food, 

fiber, and manufactured goods, and to just about 

everything else we produce and consume. Although 

water covers more than 70 percent of the Earth’s surface, only about 3 percent is fresh water—and about 

75 percent of that is inaccessible because it is locked 

up in glaciers and icecaps. 

Another important aspect of rainfall, or any other 

precipitation, is its role in redistributing the energy the 

Earth receives from the Sun. Evaporation of water from 

the Earth’s surface, condensation of water vapor into 

cloud droplets or ice particles, snow, precipitation, 

runoff of the precipitation, and melting of snow and 

ice constitute what is known as the water cycle, or the 

hydrological cycle. Evaporation, the process of changing water from liquid to gas form, absorbs 540 calories 

of energy per gram of water; while simply raising the 

temperature of a gram of water one degree Celsius— 

without changing its phase— requires only one calorie of energy. Thus, much of the Sun’s energy that 

reaches the Earth’s surface is used to evaporate water 

instead of raising the temperature of the surface. The 

resulting water vapor is carried upward by the atmosphere until it reaches a level where it is cooled to its 

condensation temperature. Then the water vapor 

releases the energy (540 calories per gram) it 

absorbed during the evaporation process. This “latent 

heat” release can occur thousands of kilometers from 

where the latent heat was originally absorbed. 

Water plays an additional critical role in weather and 

climate: water vapor, it turns out, is the most abundant 

and most important greenhouse gas! Greenhouse 

gases trap some of the energy given off by the Earth’s 

surface in the atmosphere. Therefore, the distribution 

and quantity of water vapor in the atmosphere are 

important in determining how well the Earth can emit 

the energy it absorbs from the Sun back into space. 

Unless the Earth loses as much energy as it receives, it 

will warm up. If the Earth loses more energy than it 

receives, it will cool down. The distribution of water 

vapor in the atmosphere also affects cloudiness; and 

clouds play an important role in determining how 

much solar energy reaches the Earth’s surface, as well 

as how much heat can escape to space. 

Perhaps it is now obvious that water, in all its forms, 

plays a critical role in determining what we call weather and climate. Our understanding of the complicated 

interactions involving water is insufficient to permit us 

to forecast, with much skill, weather beyond several 

days and climate beyond a few months. Because the 

occurrence of precipitation is highly variable in both 

time and space, and almost three-fourths of the Earth’s 

surface has no rain gauges because it is covered by 

the oceans, we have never been able to adequately 

observe the global distribution of rain. Measurements 

from rain gauges on islands and satellite images of 

clouds have led to estimates of global precipitation. 

But TRMM—the first satellite to measure precipitation 

with the accuracy available from a radar in combination with other remote sensors—represents a breakthrough in our ability to monitor precipitation on a 

global scale. This is already leading to improved forecasts, as shown on the next page. 

19 Investigating the Climate System: PRECIPITATION 
Appendix D: TRMM Introduction/Instruments 

without TRMM 

with TRMM 

Actual Storm Track 

Hurricane Bonnie, August 1998: 

5-Day Forecasts vs. Actual Storm Track 

Improved forecasts can save money ($600K–$1M per mile of coast 

evacuated) and lives by more precisely predicting where the hurricane 

eye will be located at landfall. Source: Dr. A. Hou, NASA DAO 

TRMM Instruments 

TRMM Microwave Imager (TMI) 

The TRMM Microwave Imager (TMI) is a passive 

microwave sensor that detects and images microwave 

radiation emitted by water droplets, ice particles, and 

the Earth’s surface. TMI detects radiation at five different frequencies, which helps to distinguish between 

rainfall, bodies of water, and land. Data obtained from 

this instrument is used to quantify the water vapor, 

cloud water, and rainfall intensity in the atmosphere. 

Precipitation Radar (PR) 

The Precipitation Radar (PR), an active sensor, is the 

first space-based precipitation radar. PR emits radar 

pulses toward Earth, which are then reflected by precipitation particles back to the radar. By measuring the 

strength of the returned pulses, the radar is able to 

estimate rainfall rates. Among the three main instruments on TRMM, PR is the most innovative. Other 

instruments similar to TMI and the Visible and Infrared 

Scanner (VIRS) have operated in space before, but 

PR is the first radar launched into space for the purpose of measuring rainfall. Data obtained from this 

instrument: 

●	 provides three-dimensional storm structures; 

●	 helps to determine the intensity and three-dimensional distribution of rainfall over land and water, 

which can be used to infer the three-dimensional 

distribution of latent heat in the atmosphere; 

●	 provides information on storm depth; and 

●	 provides information on the height at which falling 

snow or ice particles melt into rain. 

Visible Infrared Scanner (VIRS) 

The Visible and Infrared Scanner (VIRS) measures radiance in five wavelength bands (from visible to 

infrared) emitted by clouds, water vapor, and the 

Earth’s surface. The intensity of radiation from a cloud 

corresponds with the brightness or temperature of the 

cloud, which in turn indicates the height of the 

cloud—brighter (colder) clouds are higher in altitude, 

and darker (warmer) clouds are lower. In general, higher clouds are associated with heavier rain. By comparing VIRS observations with rainfall estimates from TMI 

and PR, scientists are able to better understand the 

relationship between cloud height and rainfall rate, 

and can apply this knowledge to radiation measurements made by other weather satellites. 

Cloud and Earth’s Radiant Energy System (CERES) 

The Clouds and the Earth’s Radiant Energy System 

(CERES) measures the amount of energy rising from 

the Earth’s surface, atmosphere, and clouds. Clouds can 

have both a warming and cooling effect on the Earth, 

trapping energy emitted by the Earth’s surface while 

blocking energy from the Sun. Similarly, water vapor 

also warms the Earth by trapping outgoing radiation, 

but also condenses to form clouds that sometimes 

have a cooling effect. Data from this instrument helps 

scientists learn more about how the Earth distributes 

the energy it receives from the Sun, as well as the 

effects of clouds and water vapor on the overall temperature and energy budget of the Earth. This information will help long-term climate models make more 

accurate predictions. 

Lightning Imaging Sensor (LIS) 

The Lightning Imaging Sensor (LIS) is a powerful 

instrument that can detect and locate cloud-toground, cloud-to-cloud, and intra-cloud lightning. The 

information gained from this instrument is used to 

classify cloud types and, together with other TRMM 

instruments, to correlate lightning flash rate with 

storm properties, including rainfall rate. It’s also expected that the information provided from LIS will lead to 

future advances in lightning detection and forecasting. 

20 Investigating the Climate System: PRECIPITATION 
APPENDIX F 

Florida Weather Page 

21 Investigating the Climate System: PRECIPITATION 
APPENDIX G 

Cloud Diagram 

°C 

°C 

GROUND °C 

30,000 ft. 

50,000 ft. 

25,000 ft. 

temp: -10

15,000 ft. 

temp: 0

temp: 20

22 Investigating the Climate System: PRECIPITATION 
APPENDIX H 

Glossary 

active sensor (active system)—A remote-sensing system (e.g., an instrument) that transmits its own radiation to detect an object or area for observation and 

receives the reflected or transmitted radiation. Radar 

is an example of an active system. 1 Compare with 

passive sensor. 

bright band—A narrow, intense radar echo due to 

water-covered ice particles at the melting level 

where reflectivity is at its greatest. 2 

climate—The average weather conditions in an area 

determined over a period of years. 1 

climatology—Science dealing with climate and 

climate phenomena.1 

coalesce—The merging of two water drops into a 

single larger drop. 2 

condensation nuclei/cloud nuclei—A particle upon 

which water vapor condenses. It may be either in a 

solid or liquid state. 2 

dew point—The temperature to which air must 

be cooled for saturation to occur, exclusive of air 

pressure or moisture content change. At that temperature dew begins to form, and water vapor 

condenses into a liquid. 1 

graupel—A form of frozen precipitation consisting of 

snowflakes or ice crystals and supercooled water 

droplets frozen together. 2 

hail—Precipitation composed of balls or irregular 

lumps of ice. Hail is produced when large frozen 

raindrops, or almost any particles, in cumulonimbus 

clouds act as embryos that grow by accumulating 

supercooled liquid droplets. Violent updrafts in the 

cloud carry the particles in freezing air, allowing the 

frozen core to accumulate more ice. When the piece 

of hail becomes too heavy to be carried by upsurging air currents it falls to the ground. 1 

humidity—The amount of water vapor in the air. The 

higher the temperature, the greater the number of 

water molecules the air can hold. For example: at 

60°F (15°C), a cube of air one yard (0.9 meters) on 

each side can hold up to 4.48 ounces (139.3 grams) 

of water. At 104°F (40°C), the same cube of air can 

hold up to 17.9 ounces (556.7 grams) of water. 

Relative humidity describes the amount of water 

in the air compared with how much the air can hold 

at the current temperature. Example: 50% relative 

humidity means the air holds half the water vapor 

that it is capable of holding; 100% relative humidity 

means the air holds all the water vapor it can. At 

100% humidity, no more evaporation can occur until 

the temperature rises, or until the water vapor 

leaves the air through condensation. Absolute 

humidity is the ratio of the mass of water vapor 

present in a system of moist air to the volume occupied by the mixture, that is, the density of the water 

vapor. 1 

latent heat—The amount of heat given up or 

absorbed when a substance changes from one state 

to another, such as from a liquid to a solid. 6 

meteorology—The study of the atmosphere and 

atmospheric phenomena as well as the atmosphere’s interaction with the Earth’s surface, oceans, 

and life in general. 3 

passive sensor (passive system)—A system using only 

radiation emitted by the object being viewed, or 

reflected by the object, or from a source other than 

the system. 1 Compare with active sensor. 

radar—Acronym for RAdio Detection And Ranging. An 

electronic instrument used to detect distant objects 

and measure their range by how they scatter or 

reflect radio energy. Precipitation and clouds are 

detected by measuring the strength of the electromagnetic signal reflected back. 2 

radiation/radiate—The process of giving off light, 

heat, or other radiant energy. 4 

rainfall intensity/rainfall rate—The amount of precipitation of any type, primarily liquid, per unit time. 

It is usually the amount that is measured by a rain 

gauge. 2 

23 Investigating the Climate System: PRECIPITATION 
Appendix H: Glossary 

scientific method—The scientific method is the way 

scientists get from asking a question to finding an 

answer. The general steps involved are: 

• Defining the problem 

• Stating a hypothesis 

• Making observations 

• Collecting data 

• Analyzing data, making graphs 

• Drawing conclusions based on the data 

• Reflecting on your conclusions and determining 

what you would do differently next time. 5 

Sun synchronous—Describes a satellite orbit in 

which the satellite passes over the same place on 

Earth, at the same time each day. For example, a 

satellite’s Sun synchronous orbit might cross the 

equator 12 times a day, each time at 3:00 p.m. local 

time. The satellite’s orbit is in “synch” with the Earth’s 

revolution around the Sun; therefore the area that 

the satellite is imaging is always sunlit. 1 

supercooled water—Supercooled water is water that 

remains in a liquid state when it is at a temperature 

that is well below freezing. The smaller and purer 

the water droplets, the more likely they can become 

supercooled. 2 

total ozone concentration—Refers to the concentration of ozone regardless of its form (dissolved or 

bound) in a sample. 6 

turbulence—The irregular and instantaneous motions 

of air, which is made up of a number of small eddies 

that travel in the general air current. Atmospheric 

turbulence is caused by random fluctuations in the 

wind flow. It can be caused by thermal or convective 

currents, differences in terrain and wind speed, a 

frontal zone, or variation in temperature and 

pressure. 2 

weather—The state of the atmosphere at a specific 

time and with respect to its effect on life and human 

activities. It is the short-term variations of the atmosphere, as opposed to the long-term, or climatic, 

changes. It is often referred to in terms of brightness, 

cloudiness, humidity, precipitation, temperature, visibility, and wind. 2 

1 Looking at Earth From Space Glossary of Terms NASA EP-302 

2 The Weather Channel Home Page: 

http://www.weather.com/glossary 

3 Ahrens, C. Donald. 1994. Meteorology Today. St. Paul, MN: West


Publishing Company 


4 USGS Glossary: http://interactive2.usgs.gov/glossary 

5 National Center for Ecological Analysis and Synthesis: 

http://www.nceas.ucsb.edu/fmt/doc?/frames.html 

6 USGS Water Basics Glossary: 

http://sr6capp.er.usgs.gov/GIP/h2o_gloss 

24 Investigating the Climate System: PRECIPITATION